Japanese Patent Laying-Open No. 4-295202 discloses an electric motor drive and power processing apparatus employed in an electrically driven vehicle. This electric motor drive and power processing apparatus includes a secondary battery, inverters IA and IB, induction motors MA and MB, and a control unit. Induction motors MA and MB include Y-connected windings CA and CB, respectively. Input/output ports are connected to neutral points NA and NB of windings CA and CB via an EMI filter.
Inverters IA and IB are provided corresponding to induction motors MA and MB, respectively, and connected to windings CA and CB, respectively. Inverters IA and IB are connected in parallel with the secondary battery.
In this electric motor drive and power processing apparatus, AC power is supplied across neutral points NA and NB of windings CA and CB via an EMI filter from a single phase power supply connected to the input/output port, when operating in a recharging mode, and inverters IA and IB convert the AC power supplied across neutral points NA and NB into DC power for charging the DC power supply.
The electric motor drive and power processing apparatus disclosed in Japanese Patent Laying-Open No. 4-295202 is advantageous in that an additional AC/DC converter to charge the DC power supply is not required, but disadvantageous in that switching loss of inverters IA and IB occurs when the AC voltage supplied from the single phase power supply connected to the input/output port is converted into DC voltage according to the voltage level of the DC power supply.
Further, switching control of inverters IA and IB may become complicated since the AC voltage applied across neutral points NA and NB of windings CA and CB is converted into DC voltage according to the voltage level of the DC power supply by inverters IA and IB.